2,6-Dichloro-3,5-di(secondary or tertiary alkyl)toluene which can be produced according to the present invention is known as a useful compound capable of deriving into 2,6-dichlorotoluene which is an intermediate for production of insecticidal 2,6-dichlorobenzamide derivatives or herbicidal 2,6-dichlorobenzonitrile.
Japanese Patent Application Laid-Open No. 53743/1990 discloses that 2,6-dichloro-3,5-di(1,1-dimethylethyl)toluene is obtained in high yield by chlorinating 3,5-di(1,1-dimethylethyl)toluene in the presence of aluminium chloride or ferric chloride together with sulfur, as compared with the case of chlorinating in the presence of sulfur monochloride, zinc sulfide, ferric sulfide or cupric sulfide.
Further, Japanese Patent Application Laid-Open No. 202148/1992 discloses that the yield is improved by choosing the ratio of sulfur and Lewis acid to be used.
However, since there is a demand for higher yield and the process described in the Japanese Patent Application Laid-Open No. 202148/1992 has a problem on operation because of the sulfur being poor soluble in the reaction mixture, more improvement is desired.
On the other hand, William David Watson has proposed chlorination of phenols by reacting with a chlorinating agent in the presence of a Lewis acid together with a sulfur compound (including phenyl sulfide or phenyl disulfide), by which chlorination of high para-selectivity can be conducted (Japanese Patent Application Laid-Open No. 122031/1976).
William David Watson has promptly reported the effect of phenyl sulfide described in the above proposal in Tetrahedron Lett., 1976, 2591-2594., and reported the detail including consideration in J. Org. Chem., 50, 2145-2148 (1985).
The Watson's report discloses chlorination of mono-substituted benzenes other than phenols, but the description of it is only "when chlorobenzene, toluene or ethylbenzene and isopropylbenzene are chlorinated in the presence of aluminium chloride and phenyl sulfide, both of sulfuryl chloride and chlorine produce the same ortho/para ratio" (J. Org. Chem., 50, 2147, right column, paragraph 3). Consequently, it is not found a concrete report concerning effect of coexistence of the Lewis acid and phenyl sulfide or phenyl disulfide upon chlorination of 3,5-di(secondary or tertiary alkyl)toluene.